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Re: Dataglyph findings (was: Re: Xerox supplies stego?)

daemon@ATHENA.MIT.EDU (sinster@darkwater.com)
Wed May 19 22:13:31 1999

Date: Wed, 19 May 1999 17:16:13 -0700 (PDT)
To: cryptography@c2.net
In-reply-to: <199905131226.IAA86502@alumni.rpi.edu> (message from Steve
	Furlong on Thu, 13 May 1999 08:26:59 -0400)
From: sinster@darkwater.com

Enough people expressed interest that I'm passing along my dataglyph
implementation.  I've cleaned it up and commented it somewhat.  Use as
thou wilt.

I've waited to reply to Steve's message until now so I could include
the cleaned-up dataglyph implementation.  It's stuck at the end of this
email (only 106 lines of uuencoded gzipped postscript), which is exactly
the correct place to include PostScript.

Sprach Steve Furlong <furlos@rpi.edu>:
> <<stegographic dataglyphs can be small enough to be ignored but won't
> survive faxing, or big enough to fax but can't be ignored by the eye>>
> 
> Can you make the glyphs look like an after-image from the printer's
> drum? Partial shadow images are pretty common on laser printers.

I've never seen the phenomenon to which you refer, but I'm imagining a
light gray image of previous documents appearing under a printed
document.  I suppose I could do that, but if I do I reduce the signal
to noise ratio.  That signal to noise ratio is pretty important when
it comes to the scanning step.  And if I make it too ghostly, I bet
it'll get dropped entirely (as opposed to simply corrupted) by a FAX
machine.

P.S.:
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#,   
 
end


-- 
Jon Paul Nollmann ne' Darren Senn                      sinster@balltech.net
Unsolicited commercial email will be archived at $1/byte/day.
Who is the true patriot: the man who sings the praises of a rotting land,
or he who calls your attention to the blemishes in paradise?


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